Cobalt base alloys containing titanium



Jan. 18, 1966 DUGTILITY (/o RA) YIELD STRENGTH KS l TOO J. J. RAUSCH ETAL COBALT BASE ALLOYS CONTAINING TITANIUM Filed Sept. 24, 1963 4O I700F Ti o l I 1 O 2 4 6 8 IO SOLUTE CONCENTRATION WEIGHT PERCENT TENSILE PROPERTIES OF COBALT ALLOYED WITH TITANIUM JOHN INVENTORS J. RAUSCH JOSEPH 8. Mo ANDREW 6 gIQXTTORNEY AGENT United States Patent 3,230,080 COBALT BASE ALLOYS CONTAINING TITANIUM John J. Rausch, Evauston, Ill., and Joseph B. McAndrew,

Pittsburgh, Pa., assignors, by mesne assignments, to

the United States of America as represented by the Secretary of the Navy Filed Sept. 24, 1963, Ser. No. 311,266 2 Claims. (Cl. 75-170) The present invention relates to improved cobalt alloys and to methods of making the same. More particularly, the present invention relates to cobalt base alloys having improved physical and metallurgical properties.

The present commercial cobalt alloys do not provide the strength capabilities under extreme conditions of high temperature and in a highly oxidative environment as required in the neoteric nuclear, missile and space technologies. It is necessary under these conditions to provide an alloy having high temperature oxidation resistance, high temperature strength and workability.

Accordingly, features and objects of this invention include the provision of new composition with optimum strength and acceptable oxidation resistance at high temperatures.

Another object of the present invention is to provide an alloy of cobalt that is strong and ductile, while retaining sufficient forgeability to be usefully workable.

A further object of the present invention is to provide a novel, wrought cobalt base alloy that is superior in properties to those presently used for high temperature application.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying tables and graphs wherein the figure is a graphical presentation of the effect of titanium addition on the properties of the wrought cobalt base.

The alloy which satisfies the objects of the present invention in its broadest aspect consists essentially of from 1 to weight percent titanium with the balance essentially all cobalt. The significance of titanium as a cobalt strengthener may be seen by referring to the accompanying graph. The ductility of the alloy, which may also be seen in the graph, was considered to be an important indicator of the fabricability of the material.

Although the foregoing alloys satisfy all of the objects set forth above, it was determined that by the addition of a third element to the binary alloy composition, elevated temperature strength, forgeability and oxidation resistance could be improved. The effect of ternary additions on the 1700 F. tensile properties of the base composition cobalt-l0 weight percent titanium is shown in Table I. The test alloys were aged 24 hours at 1700 F.

Table 1 Alloy YS (p.s.i.) RA. (percent) CO-IOTi-lOb 60, 000 Co-1OTl-3Ta 58, 000 27 3,230,080 Patented Jan. 18, 1966 In the preparation of the cobalt base alloys, two grades of cobalt were employed, typical analyses of which are given below:

Table II Randell Electrolytic Elements Cobalt Cobalt (percent) (percent) 99. 29 99. 6 0. 28 0. 20 0. 03 0. 05 ml 0. 01 0. 04 O. 05 0. 02 0. 03 trace 0. 04 0. O1 0. 01 0. 01

Electrolytic cobalt was found to be the more favorable base metal since this material is forgeable without the use of modifiers or special melting techniques. The alloys of the instant invention and the elements therein were, in general, of equivalent or better purity than the electrolytic cobalt. The tantalum and oolumbium used were in the form of high purity sheet.

Alloys were prepared as 250 gram, pancake shaped ingots approximately /2 x 3 in diameter.- These were ancmelted using a water-cooled tungsten-tipped electrode and a water-cooled, copper crucible in an argon atmosphere. The ingots were then hammer-forged to /2" in diameter rods from which test specimens were prepared.

Tensile tests were performed at room temperature and at 1700 F. at a strain rate of approximately 0.12 in./in./ minute. Before testing, all specimens were sealed in evacuated bulbs, treated at 1700" F. for 24 hours and aircooled.

In the present invention and dependent claims, the phrase up to shall be construed to include zero as the lower limit of the percentage range of optional elements recited.

It will be apparent that new and useful alloys having desirable characteristics and properties have been disclosed. It is therefore desired to further describe the invention as set forth in the appended claims.

What is claimed is:

1. A forgeable high-strength alloy consisting essentially of about 1 to 10 weight percent titanium, about -1 weight percent oolumbium, the balance being cobalt.

2. A forgeable alloy having high-strength at elevated temperatures consisting essentially of about 1 to 10 weight percent titanium, about 3 weight percent tantalum, the balance being cobalt.

References Cited by the Examiner UNITED STATES PATENTS 2,983,602 5/1961; L'evinson et al. 7S-170 OTHER REFERENCES Hansen: Constitution of Binary Alloys, 2nd edition,

published by McGraW-Hill Book Company, New York, N.Y., 1958, pages 51l5l4.

The Journal of the Institute of Metals, volume XLIV, No. 2, 1930, page 492.

DAVID L. RECK, Primary Examiner.

WINSTON A. DOUGLAS, Examiner.

C. M. SCHUTZMAN, R. O. DEAN, Assistant Examiners. 

1. A FORGEABLE HIGH-STRENGTH ALLOY CONSISTING ESSENTIALLY OF ABOUT 1 TO 10 WEIHT PERCENT TITANIUM, ABOUT 1 WEIGHT PERCENT COLUMBIUM, THE BALANCE BEING COBALT. 